What is the sequence of persisting for a bidirectional associations?

Is there any way to be followed when persisting relations which are bi directional? For example, I have a domain model where Persons and Events are related in a Many to Many bidirectional fashion.

A person can attend many events and a event can have a multiple persons registered and navigation from both sides is permitted.

Person.java

Event.java

In my client, I have created multiple events and persons as follows

Now my question here is, do I need to establish the relation ship after saving each of the objects or can the association be established first and persist the objects and associations.

If I can estalish the references first and then the persist, my code looks like

I have some persons who are not interested in any events and some events where nobody comes. In such a kind of requirement, how should I be modelling my pojos and configuration and how do I persist them effectively. Which should be persisted first, objects or associations? Do I need to setup the assocation between Person to Event first or Event to Person first. Is there any thumbrule, I should be aware of.

Regards
KumarRaja

subject: What is the sequence of persisting for a bidirectional associations?